Author(s): JONES, R.O., ARETA, J.L., PUGH, J.N., VAZ DE OLIVEIRA, M., LOUIS, J.B., Institution: LIVERPOOL JOHN MOORES UNIVERSITY, Country: UNITED KINGDOM, Abstract-ID: 1790

INTRODUCTION:
Carbohydrate (CHO) intake during prolonged moderate-high intensity cycling is essential for endurance performance, with current research advocating high CHO intake equal to or >90 grams/hour (g/h) in long duration events [1,2]. High CHO intake can be a challenge in race conditions, requiring regular feedings per hour, likely impacting race ‘flow’. However, the effects of different CHO ingestion patterns on substrate oxidation, physiological responses to exercise, gastrointestinal (GI) discomfort and exercise capacity have never been reported in cycling.
METHODS:
20 recreationally active males (maximal oxygen uptake 50.4±3.8 mL/kg/min) completed 2 experimental trials consisting of 180 min cycling (Lode, Netherlands) at an intensity equivalent to lactate threshold (LT; 139±29 W). 24 h pre-trial, a meal plan providing high CHO availability and standardised fat and protein intake was followed (8, 1 and 2 grams per kg of body mass respectively). Trial order was randomised with participants consuming 90 g/h of CHO, either as a 22.5g CHO gel every 15 min (CHO-15) or a 45g CHO gel every 30 min (CHO-30) of exercise. Blood glucose, lactate and GI discomfort symptoms were measured every 15 min using capillary blood samples and a visual analogue scale, respectively. Respiratory gases were collected in the last 2 of every 15 min with a metabolic cart (Vyntus CPX, UK). Stoichiometric equations were used to determine substrate oxidation [3]. Participants then completed an exercise capacity test to exhaustion at an intensity equivalent to 150% LT (209±43 W). Two-way repeated measures ANOVA was used to determine main effects and interactions for physiological data. Paired t-tests were used for exercise capacity and sum of scores for each GI symptom. Significance was set at P<0.05. All data is presented as mean ±SD.
RESULTS:
Mean CHO oxidation was similar (2.38±0.06 vs 2.33±0.07 g/min for CHO-15 and -30) for both conditions (P=0.25), which stayed consistent over time (P=0.09). Fat oxidation increased ~2-fold by 180 min of exercise (time effect, P<0.001) in both trials (treatment effect, P=0.09). Absolute oxygen uptake, blood glucose and lactate responded similarly in both trials (P=0.79, P=0.92 and P=0.34 respectively). Oxygen uptake gradually increased throughout exercise, reaching significance in the final 45 min (P<0.05), whilst glucose and lactate changed from baseline (time main effect, P<0.001). There was no significant difference between conditions for any GI discomfort symptoms (P>0.30) and exercise capacity did not differ (P=0.51) between CHO-15 and -30 (552±400 vs 612±512 seconds respectively).
CONCLUSION:
Ingesting larger CHO quantities at less regular intervals during prolonged cycling can provide a more practical approach to fuelling, with minimal impact on substrate oxidation, physiological responses to exercise, GI discomfort symptoms and exercise capacity.

References
1. Thomas et al. 2016
2. Hearris et al. 2022
3. Jeukendrup and Wallace, 2005